‘Finding Dory’ is no ‘Finding Nemo’

“Finding Dory” isn’t so much a sequel to “Finding Nemo” as it is a Looney Tunes spin-off: Wilder, sillier, broader and instantly disposable. Released in 2003, the Oscar-winning “Nemo,” the story of a father searching for his son, was only Pixar Animation Studio’s fifth movie yet remains one of its best, a marvelous feat of computer animation married to a resonant story about parenthood and coming of age.

With “Finding Dory,” co-directors Andrew Stanton (who also made the original) and Angus MacLane succumb to the trap that drags down most sequels: Instead of telling the next chapter in a story, like the “Toy Story” pictures do, they just remix the original. This time, it’s the forgetful blue tang fish Dory (voiced by Ellen DeGeneres) who embarks on a quest — finding her parents — while the father-and-son clownfish Marlin (Albert Brooks) and Nemo (Hayden Rolence) are on hand to assist.

The film’s opening 15 minutes are its best: In a flashback to Dory’s childhood, we see her parents (Diane Keaton and Eugene Levy) worry about her incapacity to retain short-term memories and teach her simple skills to help her deal with her disability. Their fear about how Dory will fare without them is understated, but it resonates with adult viewers, giving the movie the sort of emotional gravity that’s the hallmark of all great animated films.

But once “Finding Dory” jumps back to the present day, the script, which Stanton co-wrote with Victoria Strouse, resorts to the sort of improbable developments that feel like they were hammered out in a workshop, intended to justify the existence of a sequel. Dory gets an unexplained bolt of memory implying her parents are still out there. The movie, which should have properly been titled “Finding Dory’s Parents,” follows her quest to find them, hampered by her constant forgetfulness and a detour into a marine life institute in which, disappointingly, the bulk of the story unfolds.

The aquarium is the place where “Finding Dory” loses its way. Unlike the ocean, where danger lurks everywhere, the denizens here are all friendly and hospitable. Some, like the octopus Hank (Ed O’Neill), help Dory for selfish reasons. Others, such as the whale shark Destiny (Kaitlin Olson) or the beluga whale Bailey (Ty Burrell), take up her cause out of plain decency (also, they don’t have anything better to do). Elaborate escape sequences ensue, and the fish are so anthropomorphized that at one point, the octopus drives a stolen truck on the highway. I realize this is a movie about talking fish. But still.

The scale of “Finding Dory” is bigger than that of “Finding Nemo,” but I started missing the smaller, more intimate excitement of the fishing tank inside the dentist’s office in “Nemo.” The story is so thin, Dory’s memory lapses border on annoying, which is just what the character should never be. Supporting characters throw in enough comic relief to keep the film’s energy from sputtering, such as a pair of layabout sea lions (voiced by Idris Elba and Dominic West, getting along much better than they did on “The Wire”) or a loudmouth clam with stand-up comedian aspirations (voiced by director Stanton) that pops up for just one scene but almost steals the whole show.

But that’s exactly what such moments feel like: Bits of extraneous business to help a sequel justify its existence. Pixar continues to produce some marvelous, out-of-the-box movies but “Finding Dory” joins a growing number of misfires, including “The Good Dinosaur” and “Monsters University.”

“Finding Dory” is preceded by a short film, Alan Barillaro’s six-minute “Piper,” that is one of the most adorable pieces of animation I’ve ever seen, as well as a wise, funny exploration of overcoming childhood fears. The short is much more eloquent and touching than the feature-length movie that follows, even though it doesn’t contain a single word of dialogue.